It depends on how you implement the rule. An auto-hit on a healing surge, sure, I agree with you.
But, if the rule is:
Make an Endurance check = 10 + 1/2 level + core AC bonus (2 for leather, 8 for plate). If you make it, you're fine. If you miss by 5, you lose one healing surge. If you miss by 10, you lose two healing surges, etc. Endurance trained PCs often make the check. Others, not always. Plus it affects all armors Leather or higher.
This incentivizes players of most armors to train Endurance or CON. I find it amazing that PCs are walking around the world with 10 CONS and nothing bad ever happens to them shy of in combat. City slicker Wizards who never catch a cold in the wilderness. It's not a matter of making the game super realistic, it's a matter of creating a believable world while not penalizing one group of players too much over another. Sure, the Wizard in Cloth avoids this, but then again, he's is Cloth. Shy of taking a feat, taking a specific class feature, and/or a starting Int of 20, he typically has the lowest AC in the entire party, often 4 to 6 less than the heavily armored PCs. Plus, it incentivizes a Wizard player to take Unarmored Agility instead of Leather Armor (which might play into a given DM's worldview of how some classes should be).
It can also incentivize players to come up with different solutions like the Secure Shelter ritual when camping out.
While I still don't entirely agree that such a rule is necessary, I think that your version is at least a bit more balanced. Although it reads a bit like a feat tax. Take the STR/WIS Fighter, for example. He can train in Endurance, but due to the split between STR and WIS, he won't have a very high CON to buff it. This means that, at best, if he takes training in Endurance he'll only be at a -2 in Scale (possibly only a -1 or a 0 if he has a 12 or 14 starting CON). So really, you're basically making characters like that save against losing a surge, sometimes with up to a -2 modifier (or worse).
As a DM, there are other ways to encourage using CON or Endurance. Why not introduce some diseases into the campaign? Or play a Dark Sun game...then Endurance becomes
really important!
By the way, you don't think that Wizard and Cleric and other PCs aren't penalized huge for AC before they even step out of the door? You talk a lot about how the heavy AC users are penalized, but I think that there are a lot of lightly armored penalized PCs. AC is often a much more important game element than Climbing or Stealth. Not always, but often.
From my perspective, many of the heavy AC PCs get a lot of advantages over the lightly armored ones and it's not just AC. Hit points, healing surge value, number of healing surges, AND the heavily armored PCs still can often do magical sounding things like shifting multiple squares across the battlefield, or teleporting, or auto-damaging foes. One of the least balancing aspects of 4E is that the heavily armored PCs can sometimes do many of the magical sounding things that the lightly armored PCs can do, but they still get better AC and hit points and healing surges out of the deal.
Here you're confusing class and equipment. Every one of those powers can pretty much be done with a light armor character. Name any Fighter power, for example, and I can build a STR/DEX Fighter that can use it, while using light armor. Many of those powers
are present on traditionally light armored classes as well. Shifting multiple squares? Hello Ranger, Rogue, Wizard (expeditious retreat!), etc... Teleporting? Well the Swordmage, who is a Defender, does a ton of that while wearing light armor thanks to his high INT. So does the Warlock, who
also tends to wear light armor (although they can use chain, but will usually be at a lower AC than if they did a CHA/INT build in Hide).
Heavily armored PCs also do not have to bump up Int or Dex every single time, even if it is not their primary ability score. That's a real significant advantage.
As opposed to the Rogue or Ranger? Oh wait, they have DEX as a primary. Oh, well maybe the Wiz...oh wait, he uses INT. Well, maybe a melee Ranger then, they use STR as a primary, right? Oh, but then they use DEX as a big secondary for their riders...
Sarcasm aside, most of the classes that don't get heavy armor out of the box typically use INT or DEX as at
least their big Secondary stat. When they don't, they often have a way to compensate, like Dragon Magic Sorcerers (they add STR to their AC when in light armor) and Earthstrength Wardens (they add CON to their AC when in light armor). Either that, or they can very easily qualify for Chain, since you can jump up to that from Leather provided you have the right stats (which, usually you will if you don't have DEX as either a primary or a secondary).
Can you name a specific class for which this is a problem? Namely, one that does not use DEX or INT as a Primary or Secondary stat, and that also does not get proficiency in Chain? That's not a baiting or sarcastic request, I just can't think of one off the top of my head, so perhaps if we had a more specific example then we could discuss this particular problem better. If there are such classes, then yes, I would agree that they're getting the shaft.
I had a player complain when her PC was climbing down a rope and immediately got into combat, and I told her that she didn't have her weapon out or her heavy shield prepped.
Well, for one, you probably should have told your PC that she was going to have to stow those items
before she attempted the climb so she wouldn't be surprised. Secondly, the Athletics skill doesn't actually say that you need
both hands free in order to climb. Obviously you would need at least one, but since it never specifies both this might mean that your PC could've kept her shield on, and only needed to draw a weapon. That's a more iffy issue though, and would apply to the twin blade Ranger as well as any number of light armor classes.
To me, there are a wide variety of encounters in town where the PCs are not heavily armed and armored that cannot be played if the DM and players do not have a world view that, well, you are not wearing your 60 pound armor 24/7. You have to take a bath sometime. Sorry, but you cannot climb a wall with a weapon in one hand and a shield in the other, etc. As a DM, I enjoy having encounters that are not just "go to dungeon, kill monster, win". House rules like these can open up a lot of possibilities that don't often happen in games that play inside the box of the core rules only by incentivizing players to actually roleplay the PC as if it really was a person with 60 pounds of armor on his back.
I can understand what you're going for, but I think adding in additional penalties doesn't really accomplish that goal very well. The Leather wearing guy with high CON and Endurance training (Earthstrength Warden springs to mind) will just about auto-pass your check, which means that there's no incentive to ever remove his armor. If you make the penalty worse, then it just makes it worse for
everyone, while still being only a minor hinderance to the Warden (who, BTW, will probably have the highest HP and Surges of the party, and won't really mind losing one).
I just think that there are better ways to encourage this sort of play, besides adding some 3e holdover that was eliminated
for a reason. Either that, or just simply ignore it. Maybe the Fighter
wants to wear his highly polished Black Dragonscale armor to meet the King? Perhaps to remind him of when they defeated the Black Dragon plaguing his lands? The RP opportunities cut both ways, and there's a long history of heavy armor being an important status symbol and prized possession of knights...something they would've wanted to show off, not lock up in a chest every time they were in town.
